This invention relates to direct-drive manipulators and force feedback devices. More particularly this invention relates to a direct-drive manipulator having three degrees of freedom and suitable for use as a pen-based force display for a virtual reality or telerobotic environment.
A manipulator can serve as an input device for controlling movement of a robot or other real or simulated device. A direct drive manipulator responds to operator manipulations using one or more actuators directly coupled to a load (on the output side) or an operator contact point (on the input side). This contrasts with an indirectly driven manipulator which responds to operator manipulations using one or more actuators indirectly coupled to the load or operator contact point through gears or other scaling devices.
A pen-based manipulator is characterized by an elongated member having a contact point for applying operator input forces and displacements. The manipulator enables an operator holding the elongated member to move the member within a workspace under the control of manipulator components (e.g., actuators, joints and links).
A force feedback device is characterized as an output device in which forces are applied to an operator holding the feedback device. In several telerobotic applications, for example, a master manipulator located away from a robot controls a slave manipulator located at the robot. The master manipulator serves as an input device for commanding movement of the robot via forces or displacements applied to the manipulator by an operator. In addition, the master manipulator sometimes serves as a force feedback device for exhibiting force sensations felt by the operator. In a force reflection application, for example, the forces encountered by the robot under control are reflected back to the operator at the manipulator to enable improved coordination of robot motion and dexterity. U.S. Pat. No. 5,072,361 (Davis et al.) discloses a force-reflective tele-operation control system in which a master station includes an actuator exhibiting force resistance to movement in a master link. Such resistance is to be comparable to the resistance encountered by a slave device so that movement of the master device by an operator tracks movement of the slave device being controlled.
A force feedback device also is referred to as a force display. In the computer field the term display refers to a visual output device upon which ephemeral images are shown. The display serves as a visual interface between an end user and a computer environment. An operator uses his visual sense to experience the images. Analogously, the term "force display" is coined to refer to an output device upon which ephemeral forces are exhibited. The force display serves as a force-reflective, haptic, kinaesthetic, or tactile interface between an operator and a real or simulated environment. The operator uses his sense of touch to experience the forces. The force display, however, typically is more than a display in that it also serves as an input device. A force display is a bidirectional mechanical interface through which an operator both applies and receives forces and displacements.